Pressurized flow system



United States Patent US. Cl. 23230 Claims ABSTRACT OF THE DISCLOSURE Reagents are added to a continuously flowing liquid sample by maintaining a substantially constant air pressure in containers of the reagents and the sample, forcing the reagents and sample into capillary tubes, and commingling them in a mixing chamber thereafter, whereby constant ratios of sample and reagents are maintained.

This invention relates to the use of capillary tubes and air pressure to maintain low, uniform liquid flow rates. ,Specifically, it relates to methods and apparatus for commingling two or more liquids in constant ratios and uniform flow rates, as required in a continuous colorimeter.

Prior to my invention it was difficult to commingle two or more slowly flowing liquids in constant ratios, as is necessary when a sample is diluted for continuous analysis, or when various reagents must be added to a flowing liquid in proportion to its rate of flow. For example, in a continuous flow colorimeter, several reagents must be added to the sample in a fixed ratio to its flow rate before the sample enters the colorimeter. Heretofore, this was effected through the use of pumps such as peristaltic pumps driven by electrical motors. These pumps are expensive, often become plugged, cause tube ruptures, and produce a flow rate which is not constant due to the wearing out of mechanical parts.

I have discovered a method and means for producing uniform flow rates through the use of air pressure and capillary tubing which employs no pumps, electrical motors, or other moving parts. In my invention a liquid enters a flow chamber under pressure. From the flow chamber it is forced through a capillary tube by air pressure in the flow chamber. Since the liquid pressure and the air pressure are kept constant through the use of pressure regulators, the pressure of the liquid as it leaves the capillary is very precisely controlled by the size and length of the capillary. The same source of air pressure is connected to vessels containing various other liquids, which have tubes passing from the bottom of the vessels, joined to other capillaries, which are in turn joined to the capillary of the sample liquid. Thus, various liquids may be commingled in precise proportions by varying the size and length of the capillaries, despite slight variations in air pressure or sample liquid pressure. Moreover, within limits, the total flow may be changed by changing the air pressure without significantly altering the ratios.

The accompanying drawings illustrate certain specific embodiments of my invention.

FIG. 1 is a schematic drawing of the sample preparation system of a continuous flow colorimeter in which various reagents are added to a sample in proportions kept constant through the use of air pressure and capillary tubing.

FIG. 2 is a detailed sectional view of the flow chamber of the sample preparation system of FIG. 1.

FIG. 3 shows diagrammatically two flow chambers joined in such a way as to provide a constant dilution ratio of a continuously flowing sample liquid with a continuously flowing water supply.

In FIG. 1 a continuously flowing sample liquid under pressure passes through a pressure regulator 1 which reduces its pressure, through tube 2 to a flow meter or regulator 3 which keeps the flow uniform. (A pump may be used instead of the pressure and flow regulators.) The sample then passes through tube 4 to a three-way valve 5 which is first opened so that the sample will pass through tube 6 directly into the colorimeter 7 in order to flush the cell and set the instrument to zero. The dotted lines 8 and 9 provide an optional path whereby the sample may be heated in a heating coil 10 immersed in a heating bath 11 before passing into the colorimeter 7.

Once the colorimeter 7 is set at zero, valve 5 is turned so that the sample passes through tube 12 into flow chamber 13. Observing now FIG. 2, the sample passes from tube 12 through passage 14 into reservoir 15. The sample 16 rises to the top of the reservoir 15 where small amounts continuously overflow. Air under pressure passes through pressure regulator 17 and juncture 18 (FIG. 1) and, in FIG. 2 enters by tube 19 and passage 20 into the space formed by a cylinder 21 sealed to a base 22 at 23 and having a sealed lid 24. A plug 25 is provided for chemical cleaning. A mixture of air and overflowing sample passes through passage 26 and short capillary drain 27 where it is discarded. The main portion of sample leaves reservoir 15 by way of passage 28 and tube 29 and passes through three-way valve 30 and capillary 31 into juncture 32 as shown in FIG. 1.

In FIG. 1 again, the same source of air pressure applied to the flow chamber also is applied to a juncture 33 by way of tube 34 where it is slit into four sources, one passing to each of the four vessels, 35, 36, 37 and 38 by way of tubes 39, 40, 41 and 42 respectively. The four vessels 35 to 38 contain liquids A to D respectively which are forced by the air pressure respectively through tube 43 (when valve 30 permits) and capillaries 44 to 46. Liquid B mixes with the sample in juncture 32, the mixture being heated to promote a reaction in heating coil 47 immersed in heating bath 11. To this mixture is added liquids C and D in juncture 48. This final mixture is heated in heating coil 49 immersed in heating bath 11 before passing through three-Way valve 50 through tube 51 into colorimeter 7 and out drain 52. Valve 50 may be turned so that the final mixture passes through drain 53 instead of colorimeter 7. Valve 30 enables one to pass a standard solution A from vessel 35 through tube 39 and into capillary 31 instead of the sample in order to compare the sample to a standard of known concentration. The flow rate of the standard will be the same as that of the sample since both are under the same air pressure and flow through the same capillary.

FIG. 2 illustrates an example of a flow chamber. For the purposes of this invention a flow chamber is defined as any container capable of maintaining a liquid at a substantially fixed level therein and having provision for applying air pressure to the liquid whereby the liquid flows from the container under the combined pressure of the air and the weight of at least a portion of the liquid in the container.

Another variation of my invention, useful for diluting a continuously flowing sample with a continuously flowing diluting liquid while maintaining a constant ratio, is illustrated in FIG. 3. In FIG. 3 air flows under pressure through pressure regulator 60, and tube 61 into juncture 62 where it is split into two tubes 63 and 64. Pressure regulators 65 and 66 enable one to release a portion of the air pressure. The air then travels through tubes 67 and 68 respectively into flow chambers 69 and 70, similar to the flow chamber shown in detail ni FIG. 2. The diluting liquid enters flow chamber 69 by passing through pressure regulator 71 and tube 72 into reservoir 73 where a small amount continually overflows and passes out short capillary drain 74. The remaining diluting liquid passes through tube 75 and capillary 76 into juncture 77. The sample undergoes a similar journey, passing through pressure regulator 78, and tube 79 into reservoir 80. A small amount continually overflows and passes out short capillary drain 81, the remainder passing through tube 82, and capillary 83 into juncture 77, where it mixes with the diluting liquid before the mixture flows through tube 84 to the place of use.

Different ratios of dilution are obtained by altering the length and inside diameter of capillaries 76 and 83. Should extremely great ratios of dilution be desired, they may be obtained with this apparatus by releasing a portion of the air pressure with pressure regulators 65 or 66. For example should one desire 100 parts of the diluting liquid to 1 part sample, he could release some pressure through regulator 66 and adjust the capillaries 76 and 83 until the ratio is obtained.

The use of capillaries is an essential part of my invention. Capillaries function by reducing pressure and flow rates due to friction between the liquid and the capillary and the liquid with itself thereby causing a pressure drop. Thus, a length of capillary will average out minor variations in flow rate and pressure. Constrictions might serve a similar purpose, but they of necessity must be of smaller inside diameter in order to provide the same pressure drop as a relatively long capillary and therefore they are very vulnerable to plugging. Moreover, it is extremely diflicult to precisely control the size of the opening of a constriction and thereby obtain the desired ratios. With a long plastic capillary one merely cuts off a section should the pressure drop be too large or joins a small section should it be too small or substitutes a larger or smaller sized capillary. The 6 to 40 feet of polyethylene capillary preferred in the apparatus of this invention is easily coiled up and stored out of the way. It may be desirable, for some purposes, to use more than one capillary for the sample or reagents. However, generally one capillary is sufiicient. Capillaries of virtually any suitable material may be used, however polyethylene capillaries are preferred.

The actual ratios produced by a given set of capillaries may be determined in a number of diiferent ways. One may analyze the resulting mixture and determine the concentration of a known ingredient as by titration; one may simply measure the amount of liquid discharged by each capillary in a given period of time; or, conversely, measure the time required by each capillary to discharge a given amount of liquid. The preferred procedure is to measure the air pressure drop through a length of capillary compared to that of a standard. The obvious method of cutting a capillary one-fourth the length of another to obtain a four to one ratio does not always produce precise results since the inside diameter of a section of commercial capillary varies considerably and pressure drop is not linearly proportional to the length.

In the apparatus illustrated in FIG. 1, it should be noted that there are no specific requirements as to the number of reagent vessels, the number of heating coils, or the manner of combining various liquids. That is, depending on the particular analysis being conducted, it may be necessary to use more or less reagents and combine them in various different ratios and in ways to assure maximum mixing time for certain reactions. The method of my invention only requires the use of a single source of air pressure acting upon flow chambers when large amounts of continuous flowing liquids are needed or upon vessels where amounts are smaller, the outflow of which passes through capillaries before mixing in order to more precisely control ratios and flow rates.

In FIGS. 1 and 3 although pressure regulators 1 in FIG. 1 and 71 and 78 in FIG. 3 are shown, the apparatus will also operate when a positive displacement pump is substituted for one or more of these pressure regulators. The pressure regulators generally provide a constant pressure and the pumps generally provide a constant volume although a constant pressure generally will result in a constant volume and vice versa; either is satisfactory, but pressure regulators are preferred.

It is essential that the inlet pressure of a liquid entering a flow chamber be greater than the air pressure in the chamber or the liquid will not enter the chamber. The liquid pressure should not exceed the air pressure so much that it fills the flow chamber, however, but only enough to continually overflow the reservoir so that a mixture of air and liquid pass out the short capillary drain.

The drains 27 in FIG. 1 and 74 and 81 in FIG. 2 should have a short capillary affixed thereto, to retard the draining process and iron out minor variations. A minimum of air should be permitted to escape.

A flow chamber is not necessary if the sample is not a continuously flowing sample and one may use a vessel such as vessels 35 to 38 instead in such a case. However, a vessel must be refilled from time to time and thus is less advantageous where large amounts of liquids are used or when one does not wish to shut down the apparatus in order to change vessels. In addition, the pressure of the liquid leaving a vessel will become very slightly less as the vessel empties.

As an example, the apparatus of FIGS. 1 and 2 has been used for the colorimetric determination of silica in tap water. Tap water entered the flow chamber at about 8 p.s.i. and air pressure was about 5 p.s.i. The standard liquid A was p.p.b. of SiO liquid B was a mixture of sulfuric acid and ammonium molybdate, liquid C was an oxalic acid solution, and liquid D was an aminonaphtholsulfonic acid solution. Capillary size and length varied from 0.022" ID. to 0.062" ID. and 6 ft. to 40 ft. The apparatus performed excellently, and gave uniform, consistent flow rates over long periods of time Without failure.

Great precision can be achieved with these systems. Variations in the pressures upon the sample and diluting liquids as they enter the flow chambers are removed by means of the overflowing reservoir; variations of air pressure have little effect since every variation is applied equally to both liquids; and finally, the use of long capillaries enables one to precisely control the dilution ratio and maintain uniform flow rates by adding or removing small lengths of capillary or substituting larger or smaller sized capillaries.

Thus, the methods of my invention may be applied to many different variations in apparatus. It is only essential that the ratio between two or more liquids and their flow rates be controlled by having the same air pressure on the two liquids whereby the two liquids pass through capillaries before they are mixed.

I do not intend to be limited to the specific examples, apparatus, and methods disclosed herein for illustrative purposes. My invention may be otherwise practiced and embodied within the scope of the following claims.

I claim:

1. A method of commingling liquids in a substantially constant ratio comprising:

(a) applying a substantially constant air pressure simultaneously to each liquid,

(b) permitting said liquids to flow under said pressure of said air each into between about six feet and about forty feet of capillary having an internal diameter between about 0.022" and 0.062 for each liquid, and

(c) comingling said liquids as they leave said capillaries.

2. A method of adding reagents to a continuously flowing sample in a constant ratio to said sample comprising:

(a) maintaining said sample at a substantially constnt pressure and flow rate,

(b) permitting said sample to enter a flow chamber,

(c) applying air under a substantially constant pressure to said sample in said flow chamber and to each reagent,

(d) permitting said sample and each reagent to flow under said pressure or said air each into between about six feet and about forty feet of capillary having an internal diameter between about 0.022" and 0.062", and

(e) comingling said sample and said reagents after passage through said capillaries.

3. A method of colorimetrically analyzing a continuously flowing sample under pressure comprising:

(a) passing said sample under a substantially constant pressure and substantially constant flow rate into a flow chamber,

(b) applying air under pressure simultaneously to said sample in said flow chamber and to reagents used in the analysis,

(c) permitting said sample and said reagents to flow under said pressure of said air each through between about six feet and about forty feet of capillary having an internal diameter between about 0.022 and 0.062,

(d) comingling said sample and said reagents after passage through said capillaries, and

(e) passing said comingled sample and reagents through a colorimeter.

4. A method of diluting a continuously flowing sample with a continuously flowing diluting liquid comprising:

(a) passing said sample into a flow chamber,

(b) passing said diluting liquid into another flow chamber,

(0) applying air under pressure simultaneously to said sample and said diluting liquid in said flow chambers,

(d) permitting said sample and said diluting liquid to flow under said pressure of said air each into between about six feet and about forty feet of capillary having an internal diameter between about 0.022" and 0.062", and

(e) comingling said sample with said diluting liquid.

5. A method of colorimetric analysis wherein various reagents are added in a substantially constant ratio to a continuously flowing sample under pressure comprising:

(a) passing said sample through a pressure regulator and a flow regulator and into a flow chamber,

(-b) applying air under pressure simultaneously to said sample in said flow chamber and to said van'ous reagents required for colorimetric analysis,

(c) allowing said sample and said reagents to each pass through between about six feet and about forty feet of capillary having an internal diameter between about 0.022" and 0.062" under said pressure of said air,

(d) comingling said sample and said reagents and heating said sample and said reagents in an order consistent with colorimetric procedure, and

(e) passing said comingled and heated sample and reagents through a colorimeter.

6. Apparatus for comingling liquids in substantially constant ratios comprising:

(a) means for confining and separating different liquids,

(b) means for applying air of a substantially constant pressure simultaneously to each liquid,

(0) capillary lengths, at least one for each liquid, be-

tween six feet and forty feet long and having internal diameters of from 0.022 to 0.062", providing exits from said confining means, through which each liquid is forced to flow by the pressure of said air, and

((1) means for comingling said liquids after they have passed through said capillaries.

7. Apparatus for adding reagents to a continuously flowing sample liquid in a constant ratio to said sample comprising:

(a) a means for maintaining said sample at substantially constant pressure and flow rates,

(-b) a flow chamber for receiving said sample flows,

(c) means for applying air maintained at a substantially constant pressure simultaneously to said sample in said flow chamber and to each reagent,

(d) at least one length of capillary between six feet and forty feet long and having internal diameters of from 0.022" to 0.062" for said sample and each reagent through which said sample and said reagents are forced to flow under said pressure of said air, and

(e) means for comingling said sample and said reagents after passage through said capillaries.

8. Apparatus for colorimetrically analyzing a continuously flowing sample comprising:

(a) a means for maintaining said sample at a substantially constant pressure and flow rate,

(b) a flow chamber for receiving said sample,

(0) means for applying air maintained at a substantially constant pressure simultaneously to said sample and to various liquid reagents used in the colorimetric analysis, each reagent being confined in a container,

(d) lengths of capillary, at least one for said sample and at least one for each reagent, connected to said flow chamber and said containers through which said sample and said reagents are forced to flow under said pressure of said air, each capillary being between six feet and forty feet long and having an internal diameter of from 0.022" to 0.062",

(e) a means for comingling said sample and said reagents after passage through said capillaries, and

(f) a colorimeter through which said comingled sample and reagents are passed under said air pressure and analyzed.

9. Apparatus for diluting a continuously flowing sample with a continuously flowing diluting liquid maintaining a substantially constant dilution ratio comprising:

(a) a flow chamber for receiving said sample,

(b) a flow chamber for receiving said diluting liquid,

(c) a source of air under a substantially constant pressure applied simultaneously to said sample and said diluting liquid in said respective flow chambers,

(d) a capillary between six and forty feet long and having an internal diameter of from 0.022" to 0.062" connected to said sample flow chamber through which said sample is forced to flow under pressure of said air,

(e) a capillary between six and forty feet long and having an internal diameter of from 0.022" to 0.062" connected to said diluting liquid flow chamber through which said diluting liquid is forced to flow under pressure of said air, and

(f) a means for comingling said sample and said diluting liquid after each has passed through said capillaries.

10. Apparatus for conducting a colorimetric analysis wherein various reagents are added in a substantially constant ratio to a continuously flowing sample comprising:

(a) a pressure regulator for maintaining said sample at a substantially constant pressure,

(b) a flow regulator for maintaining a substantially constant flow rate for said sample,

(c) a flow chamber into which said sample passes after passing through said pressure regulator and said flow regulator,

7 8 (d) at least one container for a reagent useful in anaheated sample and reagents are passed under said lyzing the sample, air pressure and analyzed. (e) a source of air maintained at a substantially constant pressure applied simultaneously to said sample v Rafel'ellces Clted (ninbsaid fiowbchazmher fan? todsaig reagents, f t f UNITED STATES PATENTS e ween a ou SIX ee an a on ory ee 0 l 2,933,293 4/1960 Ferran 23292 XR capillary having an internal diameter between about 3,116,754 1/1964 Ferrari 23 253 XR 0.022" and 0.062" for passing said sample under pressure of said air, i (g) at least one exit length of capillary for each reagent through which each reagent passes respectively from 10 SERWIN Assistant Exammer said containers under said pressure of said air. U S Cl X R (h) means for heating and comingling said sample and .1 a

reagents after passage through such capillaries, and 23-253; l37-87, 208, 605; 14l-'-31, 105; 222-134, (i) a colorimeter through which said comingled and 15 135,145

- MORRIS O. WOLK, Primary Examiner UNITED sTATEs PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,488,154 January 6 1970 John J. Hronas It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, 'line 35, "slit" should read split Column 3, line 26, before "regulator" insert pressure Signed and sealed this 2nd day of March 1971.

SEAL Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

